1. Field of the Invention
This invention relates to a method of forming integral photography apparatus for use in obtaining and reproducing three-dimensional images of scenes; and more particularly, to a method of forming all of the components of the apparatus by a series of symmetrical and coaxial steps beginning with the use of a common multi-element molding apparatus.
2. Background of the Invention
A variety of systems for forming and viewing integral photographs have been proposed. One class of such systems, which are the subject of the present invention, involves at least two stages: in the first stage, a scene or object is photographed by exposing a sheet of photographic film through a camera consisting of a plate of transparent plastic having an array of small semi-spherical lenslets formed on its forward face, and opaque sheets with apertures formed on the same axes as the lenslets and acting as irises and field stops adjacent to or embedded within the plate. When the scene is photographed in this manner and the photographic sheet is developed, an array of images is formed, one for each lenslet, each recording the scene from a slightly different viewing orientation.
When this array of images is viewed through a screen of lenslets similar to the camera screen, the viewer perceives an integrated image of the scene in which each lenslet provides a detail of one aspect of the scene. The detail produced by each lenslet depends upon the angle of the observer's eye relative to the screen so that the observer's two eyes produce a stereoscopic image, giving the feeling of depth. As the viewer's head moves relative to the screen the contribution to the integrated picture provided by each lenslet changes so that the observer effectively views the photographed object from different angles, exactly as if viewing the object itself. This effect may be referred to as "look around".
As originally proposed, the integral photography method produced a pseudoscopic image of the scene, i.e. where there is a reversal of the depth along the visual axis relative to the actual image of the scene. It was later proposed that an intermediate process step be interposed between the taking and viewing of the integral photograph. In this intermediate or "printing" stage, each elemental image on the photographic medium is rephotographed through the lenslet of an array to achieve a conversion of the pseudoscopic into a proper orthoscopic positive.
The apparatus required for this three step process thus consists of a camera, a printing apparatus, and a viewing screen. The same lenslet array used in the camera can be employed to advantage in the printing operation but a separate lenslet array must be used in the viewing screen since the focal length of the camera lenses is designed for paraxial rays while the focal length of the lenslets of the viewing screen is designed for predominantly off paraxial and marginal rays. Furthermore the lenslets of the viewing screen desirably contact one another while the lenslets of the camera are spaced from one another. The camera employs at least two, and preferably three opaque sheets formed with arrays of holes arranged on the same axes as the lenslets. These sheets act as irises and field stops and may be formed of a rigid material to reinforce the camera structure.
A complete system for taking, printing and viewing integral photographs thus requires a plurality of components each formed on a planar array and having a very precise dimensional relationship to the other component arrays. The problem of producing all of these components with the required precision of relationship relative to one another is complicated by the interaction between the nature of the materials which must be employed for the lenslet arrays and the effects of the required processing steps on the dimensions of these materials. Particularly, because of considerations of transparency and index of refraction, the choice of material for the lenslet-containing plates is limited to a few plastics. Moreover, these plates would be very difficult to produce by any processes other than thermal molding or casting. Both of these processes result in shrinkage of the material so that the completed arrays are on different centers than the masters used to form the array.
As a result of these and related factors, it is extremely difficult to produce adequate apparatus for taking, printing, and viewing integral photographs. This is even more difficult if the parts are to be produced with a production process that will result in a relatively low cost operation.